Cyclodextrin inclusion complex formation with butylated hydroxytoluene and its application in polyethylene film

Abstract

AbstractThe phenolic antioxidant, butylated hydroxytoluene (BHT), is added during polymer processing to protect polymers from oxidative degradation. Because of its high‐volatility, it is susceptible to loss through volatilization in high‐temperature processing. Cyclodextrin (CD) inclusion complexation (IC) with volatile compounds can prevent losses of volatile compounds, because of volatilization. In this study, BHT was successfully included in β‐CD and its complex was confirmed using Wide‐Angle X‐ray Diffraction (WAXD), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), and Nuclear Magnetic Resonance spectroscopy (NMR). Low‐density polyethylene (LDPE) films with BHT itself and BHT‐β‐CD‐IC were produced on a pilot plant scale. After extrusion, it was found that 44 and 78% BHT was lost from the BHT‐β‐CD‐IC LDPE and BHT LDPE films, respectively. Hence, the complex proved to be more efficient in preventing loss of BHT, because of encapsulation of volatile BHT. In addition, microscopy studies indicate that BHT‐β‐CD‐IC LDPE film shows small aggregates, uniformly distributed in the LDPE matrix over a large range. The BHT efficiency of the complex in the film was measured using DSC for determining the oxidation induction time. The oxidation induction time (OITtime) was 35 min for the BHT‐β‐CD‐IC LDPE film as compared with 16 min and 26 min values of LDPE and BHT LDPE films, respectively. Hence, the encapsulation of BHT in β‐CD maximizes the efficiency and stability to thermal degradation for BHT‐β‐CD‐IC LDPE film. The viscoelastic behavior of the films was also studied using dynamic mechanical analysis. The results indicate increases in storage modulus (El) and loss modulus (Ell) of the complex and a shift in the maxima of tan δ (Ell/El) to lower temperature in the LDPE films processed with BHT, β‐CD, and BHT‐β‐CD‐IC. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010